The invention relates to a process for heating a solid metal alloy workpiece to a final temperature lying between solidus and liquidus temperature of the alloy, in particular for producing a part solid-part liquid, thixotropic state for the workpiece.
When producing metal alloy phases having thixotropic properties, it is known to set the temperature of an alloy melt to a value between solidus and liquidus temperature and to vigorously stir the alloy paste thus produced to convert the dendrites forming in the solidification process to form essentially globular cast grains. This process and the possibilities for using the metal alloy phase having thixotropic properties thus produced are described in detail, for example in U.S. Pat. No. 3,948,650 and U.S. Pat. No. 3,959,651.
These part solid-part liquid metal alloy phases are generally initially cooled below the solidus temperature of the alloy, generally to room temperature, and heated only shortly before further processing thereof to the required processing temperature, at which the thixotropic properties appear.
Coarsening of the cast grains is undesirable both in the production of the metal alloy phase having thixotropic properties and in the later repeated heating of the workpieces to the further processing temperature.
It is generally known to use oil, gas or resistanceheated furnaces with or without circulation of air, or even induction furnaces, to heat metal materials.